Conventional processors include one or more arithmetic logic units for performing iterative operations such as divide, square root and transcendental (e.g., SIN, COS) operations. Iterative arithmetic operations are conventionally executed until a result is produced that has a fixed, defined bit precision. That is, operands are iteratively processed to produce a result having full precision, i.e., a target precision such as the precision associated with a result register or a precision associated with the starting operands. For example, the Institute of Electrical and Electronics Engineers (IEEE) has defined a standard associated with binary floating-point arithmetic, often referred to as IEEE 754. The IEEE 754 standard specifies number formats, basic operations, conversions, and exceptional conditions relating to both single and double precision floating-point operations.
IEEE 754 compliant floating-point numbers include three basic components: a sign bit, an exponent, and a mantissa. The mantissa is further broken up into an integer portion and a fraction portion. Only the fraction bits are stored in the encoding. For normal numbers, the integer portion is implicitly equal to the value of 1. IEEE 754 compliant single precision numbers are represented by a sign bit, an 8-bit exponent and a 23-bit fraction while double precision numbers are represented by a sign bit, an 11-bit exponent and a 52-bit fraction. As such, iterative processing of IEEE 754 compliant floating-point numbers produces results having 24-bit precision for single-precision operands and 53-bit precision for double-precision operands. For example, a processor equipped with a single-precision IEEE 754 compliant ALU produces results having a full precision of 24 bits. However, certain applications, such as openGL compliant graphics applications, may not require results having full 24-bit single precision. As such, unnecessary power and processing cycle consumption occurs by calculating results to full 24-bit single precision for applications that can tolerate something less than full single precision, e.g., 16-bit precision.
Some conventional processors produce results having a precision less than that of the target format. However, these processors terminate iterative arithmetic operations short of the target format only when the operands being acted on have a precision less than the target format. For example, a double-precision processor can perform a single-precision operation on single-precision operands, producing a single-precision result, even when the target register format is that of a double-precision value. As such, some conventional arithmetic processes are operand-precision dependent, and thus, produce results having a full precision equivalent to that of the operands. As a result, power and processor cycles may be unnecessarily consumed to produce results having a precision greater than that which may be tolerable or acceptable for certain applications.